1. Field of the Invention
The present invention relates to a reflective-type liquid crystal display panel without backlight, and a method for producing same.
2. Description of the Prior Art
The recent rapid development of liquid crystal display panels has paved the way to applications in many fields such as word processors, lap-top personal computers, and portable televisions. A special attention is being paid to a reflective-type liquid crystal display device without backlight, because the display device without backlight is lightweight, thin, and consumes less power.
In conventional reflective-type liquid crystal display panels a TN (twisted nematic mode) or a STN (super-twisted nematic mode) are used. In these modes a linear polarizer is necessarily used, but under the polarizer, half of the natural light is wasted in the display. Thus, even if an intensified natural light is used, the image display tends to be dark.
In order to solve this problem, a special mode is proposed for fully utilizing the natural light. For example, a cholesteric-nematic phase-change type guest-host mode is proposed by D. L. White and G. N. Taylor ("J. Appl. Phys." 45, Page 4718, 1974). In this guest-host mode, a cholesteric liquid crystal, which is a host liquid crystal, tends to change to a nematic phase under its own electric field. A reflective-type multicolor display device is also proposed, which is a phase change type guest-host system equipped with a micro color filter ("Proceedings of the SID", vol. 29, page 157, 1988).
In order to display a brighter image in the mode in which no polarizer is needed, it is essential to intensify the light which tends to scatter perpendicularly to the screen. To achieve this, it is essential to control the surface roughness of the reflection plate. The second-mentioned literature teaches that the surface of a glass substrate is roughened by abrasives and then the roughened surface is etched with hydrofluoric acid for a controlled period of time, thereby securing an adequately flattened surface. The flattened surface is covered with a metal thin layer such as an Ag layer.
However, the problems are that the reflective surface of the glass substrate must be first roughened by abrasives, thereby making it difficult to secure a uniform surface of the substrate. In addition, such rugged surfaces makes it difficult to reproduce the same pattern.